x86: Init per-cpu shadow copy of CR4 on 32-bit CPUs too

[ Upstream commit 5b2bdbc84556774afbe11bcfd24c2f6411cfa92b ]

Commit:

   1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")

added a shadow CR4 such that reads and writes that do not
modify the CR4 execute much faster than always reading the
register itself.

The change modified cpu_init() in common.c, so that the
shadow CR4 gets initialized before anything uses it.

Unfortunately, there's two cpu_init()s in common.c. There's
one for 64-bit and one for 32-bit. The commit only added
the shadow init to the 64-bit path, but the 32-bit path
needs the init too.

Link: http://lkml.kernel.org/r/20150227125208.71c36402@gandalf.local.home
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20150227145019.2bdd4354@gandalf.local.home
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index e757fcbe90dbc7906235ab88b4302086e9f1fd82..88635b30169493eaa2581d3db6a4e0fd92855476 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1405,6 +1405,12 @@ void cpu_init(void)
 
        wait_for_master_cpu(cpu);
 
+       /*
+        * Initialize the CR4 shadow before doing anything that could
+        * try to read it.
+        */
+       cr4_init_shadow();
+
        show_ucode_info_early();
 
        printk(KERN_INFO "Initializing CPU#%d\n", cpu);